1. Field of the Invention
This invention relates to a method of continuously copolymerizing ethylene and vinyl acetate in a solvent.
2. Description of the Prior Art
Various methods are known for the polymerization of vinyl monomers. In the case of vinyl acetate polymerization, continuous polymerization methods have been widely employed because of advantages achieved thereby with respect to productivity and uniformity in product quality. Generally, said polymerization reaction, when conducted on a continuous basis, tends to cause polymer and gel formation and accumulation, for instance, on the polymerization vessel wall and in the so-called "dead space" within the vessel where the feed stream becomes sluggish, whereby the heat transfer coefficient is rapidly decreased. Under such circumstances, difficulties arise which render continuous operation over an extended period virtually impossible. Thus, for example, removal of the heat of polymerization becomes extremely difficult or the discharge of the gel-like substances causes line clogging. Cleaning of the polymerization vessel at relatively short time intervals becomes essential, and the advantages of continuous polymerization become severely diminished. Also, in the solution polymerization of ethylene-vinyl acetate co-monomer systems, which is carried out in a homogeneous phase, the formation of gel-like substances and the accumulation thereof causes great difficulties.
The inhibition of gel formation and accumulation has thus been one of the important problems awaiting solution from the viewpoint of stable continuous operation over a long period of time.
To date, there have been no effective methods developed for the prevention of gel formation within the polymerization vessel.